Decentralized Robust Control of Robotic Manipulator in Joint Space Based on Torque Feedbacks

A decentralized robust control algorithm for robotic manipulator in joint space is proposed, in which the linkage and its joint driver are treated as a module with a torque sensor installed on its driver shaft connecting the successive module. Due to the coupling between two connected dynamic modules can be measured by the torque sensor, the computation of the nonlinear coupling effect caused by the rest upper linkages is no longer needed, which means the complexity of the dynamic equations of the manipulator will be greatly reduced and the real-time compensation calculation of manipulator dynamics is not required in its control loop. Furthermore, the joint torque sensor enables the feedback of the external disturbance and gravity load acting on the linkage, which equips the control system with a strong anti-interference capability. Since there is no need to compute the feedforward compensation joint torque, the structure of the control system becomes simple and the joint controller can be independently designed. An integral adaptive compensator is specifically designed to deal with the compensation of the dynamic coupling from the low linkages because such coupling cannot be sensed by the joint torque sensor. A robust control strategy was proposed to compensate for the friction parameter variation between the modules of the manipulator and the uncertainty caused by the reconfiguration of the manipulator. The computer simulation is conducted to verify the effectiveness of the proposed control algorithm.